Improved optical combination



p 6, 1935. J. T. F. CONT] IMPROVED OPTICAL COMBINATION 2 Sheets-Sheet 1 Filed Dec. 11, 1934 II II o V W w W lllqx j 1 A ril 16, 1935. J. T. F. CONTI.

IMPROVED OPTICAL COMBINATION Filed Dec. 11, 1934 2 Sheets-Sheet 2 gfmwilm Patented Apr. 16, 1935 UNITED STATES. PATENT OFFICE DVIPROVED OPTICAL COMBINATION James Tiburce Felix Conti, Paris, France, as-

signor to Socit pour lE'clairage Bationnel Sper, Paris, France, a French company Application December 11, 1934, Serial No. 757,025

In France December 1, 1933 1 Claim. (01.176-34) The invention has for its object an optical of light has two boundary rays and 12, while combination which provides a pencil or beam or the second part 3 oi. the reflector provides the light to be obtained that is flattened and wider pencil wh as t undary rays a and 0- than with prior devices and can be carried into It will therefore be seen that the part of the client by the construction of an incandescent pen il l a d t d hasali ht d ns ty 5 electric lamp. equal to the sum of those of the pencils which According to the invention,arefiector is formed originate from the tw parts of t e fl c 2 by a surface of revolution generated by the rotaa d 3, While the P between b and c 1S 1858 tion about a vertical axis of a suitable curve havil umi teding two difi'erent foci. This reflector is combined By suitably selecting the relation of the focal 10 with a source of light arranged on an arc of a lengths of two parabolic branches of the curved circle located in the plane containing the foci. line, as well as the position of the source of light,

In cases where the curve is formed by two the form of the light beam, as well as the dimenbranches of a parabola having respectively difsions and the intensities of illumination oi. the

5 ferent focal lengths, the source of light can be surfaces ab and be may be modified. arranged between the foci. As shown in Fig. 3, the bulb I is formed by the The invention thus defined may be carried into rotation of the two parabola branches 2 and 3 efiect very simply and economically by a simple about a vertical axis XX. These two parabola incandescent electric lamp having a bulb having branches have their foci at f and respectively.

2 two adjacent reflecting surface portions, said When the source of light at 4 is located between portions beingof the shape of a part of a surface the two foci f F, the reflected light rays will all of revolution generated by a planar curved line be directed below horizontal planes passing of two parabolic portions moving about a comthrough the difierent reflecting points of the remon axis of revolution, the two parabolic portions flector. As the reflecting suriace of the bulb is having difiering focal distances, combined with formed by the rotation of the curved linev 2-3, 25 a filament arranged on an arc of a circle and it is evident that the foci will not be points, as is placed as has been stated, the part of the bulb the case in ordinary head-lamps, but circles of containing the source of light being silvered to foci f and f concentric to the wall 5 of the bulb. constitute the reflector. This mode of carrying The filament 6 will then be arranged on a curved out the invention enables a true head-lamp to line concentric to the axis of revolution and sit- 30 be obtained with a simple incandescent electricuated between the two circles of foci f and f lamp. It will be supported, for instance, by three sup- .In order to enable the invention to be better ports I, 8 and 9 fixed on a foot l0. understood, reference will be made to the accom- The arrangement of the three supports and of panying drawings, which show, by way of exthe filament permits the same bulbtobe mounted 35 ample, how the invention may be carried out. either for leading in the current through the cen- Figure 1 shows diagrammatically the optical tral support 8 and connecting the supports 1 and efiects in a system according to the invention. 9 in multiple, which permits a given voltage to Figure 2 is a transverse section of the light be employed, or for leadinginthe current through pencil or beam as viewed some distance in front the supports 1 and 9 and maintaining the supports 40 of the lamp. 8 insulated, which gives a bulb utilizable for volt- Figure 3 is an elevation, partly in section, of ages twice as great as with the former multiple the lamp according to the invention, and connection.

Figure 4 is a plan view of this lamp taken on The optical combination thus obtained gives a the plane of the filament. luminous beam or pencil which is flattened and 45' In Figure 1, the numerals 2 and 3 indicate the wider than with certain prior devices and thus two parabolic branches of the curved line has great advantages and permits of numerous which have generated the reflector shown in applications; for example, a lamp thus conon in Fi u e Ea h of these two branches structed and placed on a motor-car will illumi- 0f the curved line has its i d idua focus f or f, nate the road over a great width with the advanthe light source being placed between the two tage of directing all the light toward the ground foci at 4. and avoiding dazzle.

Tracing the path of the light rays emitted by Also the quantity of light produced by the the source 4 and reflected by the part 2 of the relamp according to the invention is distributed flector, it will be seen that the pencil or beam in an advantageous manner and enables wide 55 surfaces to be illuminated, which is of great advantage in illuminating, for instance, a platform, by arranging a small number of lamps in the troughs employed in indirect lighting.

An optical system of this kind will produce an advantageous oblique illumination of surfaces. Thus, if such a surface is represented by the line a, d, Fig. -1, it will be seen that the more distant points are illuminated by the more intense part ab of the light beam, while the nearer points are illuminated by the weaker part be; the illumination of the surface is thus rendered uniform and rational.

I declare that what I claim is:- An electric lamp comprising a bulb having two I adjacent reflecting surface portions, said portions being of the shape of a part of a surface of revolution generated by a planar curved line of two parabolic portions moving about a common axis of revolution, the two parabolic portions having differing focal distances, and. a filament constructed and arranged as the arc of a circle concentric to said axis of revolution and located 10 between said tool.

JAMES TIBURCE FELIX CONTI. 

